A backlight module provides a light source for a liquid crystal display (LCD) and is an important component of the LCD.
A conventional backlight module includes a light guide plate and a reflective sheet located on a side of the light guide plate away from a light exiting surface. The main function of the reflective sheet is to reflect light transmitted from the light guide plate back to the light guide plate, so as to enhance the brightness of the backlight module. The reflective sheet is a monolithic film, and the reflectivity of the entire film is substantially uniform in different regions, so that the light reflected to the light guide plate is substantially uniform in every regions.
Local brightness control is to control the brightness of the backlight in a localized manner. It is significant for improving dynamic range of the display, improving region contrast, and achieving a high-dynamic range (HDR).
When the brightness of the conventional display backlight module needs to be adjusted, the brightness is usually changed by adjusting the light source. However, this way of adjusting brightness causes the brightness of the entire light exiting region to be increased or decreased at the same time, which cannot achieve localized control of brightness.